1. Technical Field
The present disclosure relates to orthopaedic prostheses and, more particularly, to provisional orthopaedic prosthetic components that can be used to facilitate the intraoperative selection of one of a set of differently configured permanent prosthetic components.
2. Description of the Related Art
Orthopaedic prostheses are commonly utilized to repair and/or replace damaged bone and tissue in the human body. For example, a knee prosthesis may include a femoral component which replaces the articular surface of one or both of the natural femoral condyles. Frequently, the femoral component articulates with a tibial component attached to the proximal end of the patient's tibia, so that the knee prosthesis completely replaces the articular surfaces of the natural femur and tibia.
During a conventional surgical procedure to implant a knee prosthesis, a provisional femoral component and a provisional tibial component may be placed on a resected distal femur and resected proximal tibia, respectively. The provisional components are used to ensure proper fit of the prosthetic components upon their respective resected surfaces prior to implantation of the permanent component, and may also be used to assess the kinematic profile (e.g., range of motion, ligament/tendon tension, etc.) expected of the knee prosthesis after implantation. To this end, provisional components are typically provided in a range of sizes and/or configurations, with each size substantially identical to a corresponding permanent prosthetic component. In some prosthesis systems, a wide range of sizes is available with a relatively small size difference between adjacent sizes. This “fine resolution” in the range of sizes seeks to ensure a proper fit of the implant on the bone, and to optimize the interaction between the implant and adjacent components and anatomic structures. Moreover, providing many implant sizes facilitates knee replacement surgery for the widest possible variety of patient anatomies.
In surgery, instrumentation for an initial resection of the bone is typically chosen based upon known characteristics of the preoperative bone, such as may be ascertained by preoperative imaging, intraoperative measurements, and the like. Alternatively, the instrumentation may be chosen intraoperatively after the bone is exposed, based on a surgeon's assessment of the most desirable resection profile for a given patient. A first provisional component corresponding to the particular size and geometry of the initial resection is then selected, and is attached to the femur and/or tibia after resections appropriate to the chosen trial component sizes are completed.
The fit of the provisional component is then evaluated, and the knee prosthesis may be articulated through a range of motion to assess kinematic characteristics of the new prosthesis, such as ligament tension throughout the range of motion. If the kinematic characteristics are undesirable, or some parameter of prosthesis fit is incorrect, a differently sized tibial and/or femoral component may be selected. In some instances, the differently sized component requires recutting or otherwise modifying the distal femur after the first provisional component is removed. Substantial design efforts have been focused on providing instrument guides suitable for performing such additional cuts or modifications, such as instrument guides including pins, screws or other attachment mechanisms for connecting the guides to the previously resected distal femur.
Once the femur has been recut to accept the new size of provisional component, the new component is attached to the femur and the provisional knee prosthesis is again articulated throughout a range of motion to assess kinematic characteristics and other fit characteristics. If undesirable kinematic and/or fit characteristics persist, additional prosthesis sizes may be chosen—and further resection of the distal femur to accommodate the differently sized provisionals performed as needed—until an acceptable prosthesis is found.